Swine dysentery is a mucohemorrhagic, diarrheal disease that affects primarily weanling pigs, but may affect larger pigs. The disease is often referred to as bloody scours, bloody dysentery, hemorrhagic dysentery, and mucohemorrhagic diarrhea. The disease occurs in many swine-raising areas of the world.
Morbidity is usually greater than 90 percent in weanling pigs and mortality may reach 75 percent. Experimentally, swine dysentery may decrease the rate of weight gain twofold and decrease efficiency of feed conversion threefold, as compared with uninfected control pigs. The disease causes tremendous financial losses because of death and decreased rate of growth of infected swine.
The cause of swine dysentery is, as yet, ill defined. In the past, Vibrio coli was believed to be associated with the disease. More recently, a large spirochete Treponema hyodysenteriae, acting in association with other intestinal microorganisms, is thought to be the cause of the disease. At present, the only reliable method of experimental reproduction of the disease is to inoculate susceptible pigs with colonic mucosa and colonic contents of pigs acutely affected with the disease.
The outlook for successful prevention and control of swine dysentery has not been promising because no product previously approved for use in the United States has satisfactorily treated the disease. Many swine owners have ultimately had to depopulate, clean, disinfect, and restock when the disease became enzootic. It appears that any immunity that develops from natural infection is short lived, and little optimism is expressed concerning the early development of a useful immunologic agent or vaccine.